1. Field of the Invention
The present invention relates generally to a method of determining the air temperature in the intake manifold of an internal combustion engine and, more particularly, to a method of defining a dynamic temperature model that predict the temperature of the air in the intake manifold of an internal combustion engine based on thermal transfer and vehicle parameters of the engine.
2. Discussion of the Related Art
Most internal combustion engines associated with a vehicle incorporate a temperature sensor positioned within the intake manifold of the engine to determine the temperature of the air entering the engine cylinders, sometimes referred to as the engine charge air temperature. This temperature measurement is important to provide the signals that control fuel and spark to the cylinders at the appropriate time for proper and efficient operation of the engine. Because colder air is more dense than hotter air, the amount of air charge in the cylinders is different depending on the charge air temperature, and thus the application of fuel and spark to the cylinders needs to vary depending on this temperature. In other words, the charge temperature is critical because this temperature determines the charge air quantity entering the cylinders regardless of the different ambient conditions. The charge temperature thus affects automatic idle speed (AIS), knock, start fuel and on-board diagnostics (OBD) features of the engine. Currently, a "speed-density" method is used for the fuel control. In combination with MAP and RPM readings, the charge temperature is used to determine the fuel injection pulse width control signal.
FIG. 1 depicts an engine control module 10 including a central processing unit (CPU) 12. A number of sensor inputs are applied to the CPU 12, and outputs from the engine control module 10 control certain operations of the vehicle engine, as is understood in the art. An ambient temperature measurement is currently provided to the engine control module 10 to control the engine radiator fan, A/C, exhaust gas recirculation (EGR), target idle speed, purge, O.sub.2 sensor diagnostics and start fuel controls. It has been determined that a relationship exists between the ambient air temperature and the charge temperature. However, current vehicles incorporate separate temperature sensors to measure both.
Temperature sensors are known, such as thermocouples, that can give highly accurate temperature measurements of the engine charge temperature. However, the type of temperature sensor generally positioned within the intake manifold is typically an inexpensive heat resistive element whose accuracy is limited.
What is needed is a technique for determining the charge temperature of the air in the intake manifold of an internal combustion vehicle that does not require a dedicated charge air temperature sensor, so as to eliminate the cost of the sensor and improve charge temperature accuracy. It is therefore an object of the present invention to provide such a technique.